Planaria

Planaria is a genus of planarians in the family Planariidae. Due to its excellent ability to regenerate, species of Planaria has also been used as model organisms in regeneration studies. When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual. When decapitated, they retain their memories. Various species of Planaria have been widely used as model invertebrate organisms in pharmacological research, in particular in the studies of the drugs of abuse. They were also proposed as models in toxicological research. Wikipedia